An optical module with a mirror including a plurality of individual mirrors, which can be displaced by actuator, is known from U.S. Pat. No. 6,658,084 B2.
During operation of an illumination optical system for microlithography projection exposure system, thermal energy can be deposited in the individual mirrors, in particular during operation with EUV (Extreme Ultra Violet) radiation in the range between 5 nm and 30 nm. In some cases, such systems can be operated only with an intolerably low radiation output for demanding illumination tasks. In certain cases, such systems can be operated only with intolerably high losses with regard to the radiation throughput (with regard to the ratio between the used and the produced EUV radiation).